authors - cityofsydney.nsw.gov.au · web viewlloyd, a., law, b. and goldingay, r. (2006). bat...

Insectivorous Bat Survey for City of Sydney Local Government Area (2016-17)

City of Sydney Town Hall House 456 Kent StreetSydney NSW 2000

1 / Insectivorous Bats in City of Sydney LGA

First published June 2017

AuthorsLeroy Gonsalves and Bradley Law – Department of Industry, Lands & Forestry.

Cover image: Sydney Park Wetland 4


ContentsExecutive summary......................................................................................................3

Introduction..................................................................................................................4

Methods.......................................................................................................................5

Results.......................................................................................................................10

Discussion..................................................................................................................17

References.................................................................................................................23


Executive summaryA survey of insectivorous bats in selected green spaces within the City of Sydney local government area (LGA) was undertaken between November 2016 and April 2017. Acoustic detectors were used to record the echolocation calls of bats at 12 sites in spring 2016 and autumn 2017. Five insectivorous bat species were identified, all of which were previously recorded in the LGA. Two of these species are listed as vulnerable under the NSW Threatened Species Conservation Act 1995. The Eastern Bentwing Bat (Miniopterus schreibersii oceanensis) and Gould’s Wattled Bat (Chalinolobus gouldii) were the most commonly recorded species. Nightly species richness was greater in autumn relative to spring, as was total bat activity which reflected increased activity by M. schreibersii oceanensis and C. gouldii in this season. Locating the roosting sites of these species, particularly M. schreibersii oceanensis, should be prioritised to facilitate future management of these species. These activity data provide a quantitative base-line that can be used for comparison as part of any future monitoring.


IntroductionA major cause of decline in biodiversity is the loss and fragmentation of habitat resulting from urban development (Garden et al. 2006). Remnant bushland in urban areas often occurs in small patches and can be highly fragmented, with a lack of connectivity between these patches (New 2002; Stenhouse 2004). In some highly urbanised areas, remnant bushland is absent from green spaces within the urban matrix. Despite this, green spaces in urban areas have been found to support a diverse suite of plant and animal species (How and Dell 1994; Parsons et al. 2003). Consequently, sound management of these habitats is of importance to maintain functioning ecosystems within the urban matrix.

The importance of green spaces and the fauna they support has been recognised by the City of Sydney Council (City), with fauna a key focus area in the council’s Urban Ecology Strategic Action Plan (UESAP). Specifically, the UESAP has established an aim to increase the distribution and abundance of priority fauna species across the local government area (LGA) from a baseline set in 2012. Baseline data were determined through fauna surveys undertaken within parks and other public land throughout the LGA in late 2010 and early 2011. In addition, records from insectivorous bat monitoring by council volunteers, online surveys and other reports made between October 2010 and March 2012 were also included in the baseline fauna list for the LGA.

To assist with future management of fauna in the LGA, the City requested a fauna survey to be undertaken to document the distribution and activity of priority fauna species. Insectivorous bats are one diverse fauna group that use echolocation to navigate their habitat and detect prey (mostly insects such as moths, beetles and flies) (Churchill 2009). At least 18 insectivorous bat species have been recorded in the Sydney Basin (Basham et al. 2011; Threlfall et al. 2012a), of which eight are listed as threatened species in New South Wales. These species are known to roost in tree hollows or subterranean structures (e.g., caves, mine adits/shafts and stormwater culverts) (Churchill 2009).

In September 2016, the City’s Urban Ecology Coordinator commissioned researchers from the NSW Department of Industry, Lands and Forestry to establish a comprehensive baseline dataset of insectivorous bat species in the LGA. The survey targeted selected green spaces within the City of Sydney LGA and was undertaken in spring and autumn to sample seasonal variation in the activity of echolocating bat species. The aim of the survey was to document insectivorous bat species and their distribution within key habitats in the City of Sydney LGA.


MethodsStudy areaThe study was carried out in the City of Sydney LGA, NSW. The LGA is small (2640 ha), but highly urbanised and extends from St Peters and Rosebery in the South to Pyrmont and Rushcutters Bay in the North, and is home to ~205 300 people. Very little bushland (13.3 ha) occurs in the LGA, with that remaining being highly fragmented and restricted to green spaces that are surrounded by extensive urban areas. Despite this, green spaces within the LGA supported up to 99 fauna species, including at least six insectivorous bat species, in the baseline set in 2012.

Sampling sites and designOf nine sites identified by the City’s Urban Ecology Coordinator, eight were included in surveys (Figure 1). One site (Beare Park) was not included given its close proximity to Rushcutters Bay Park and small size. Four additional sites were identified by the authors in collaboration with the City’s Urban Ecology Coordinator, with sites selected to be representative of the variation in green space present within the LGA, but also to maximise the diversity of bats surveyed (Figure 1). One of these sites (Centennial Park) occurred outside the City of Sydney LGA, but was included given its close proximity to the boundary of the LGA and the likelihood of movement of bats across LGA boundaries. Survey sites included green space (Figure 2a) and waterways (Figure 2b) within or near green spaces. Waterways are known to be areas of high bat activity and are selectively used by particular insectivorous bat species (e.g., Large-footed Myotis, Myotis macropus). The area of green space within each sampling site ranged from 0.7 ha – 54 ha (Table 1). Each site was surveyed in spring (November 2016) and autumn (April 2017).


Figure 1. Location of sampling sites (red dots): 11 sites in the City of Sydney LGA (blue boundary) and one site (Centennial Park) in the Randwick LGA (red boundary).

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b)


Figure 2. Examples of (a) green space (Sydney Park) (b) waterways (Woolloomooloo Bay) sampled in the survey.


Table 1. Sites surveyed in spring 2016 and autumn 2017.

Site Habitat Area of green space (ha)Alexandria Canal Waterway N/AFederal Park Green Space 13.5Kimberley Grove Reserve Green Space 0.7Centennial Park Waterway N/ARushcutters Bay Park Green Space 6.4Rushcutters Canal Waterway N/ASydney Park Green Space 41.6Sydney Park Wetland 4 Waterway N/ASydney University Green Space 54Victoria Park Green Space 9Waterfront Park Green Space 1Woolloomooloo Bay Waterway N/A

Bat surveysBat activity was surveyed for up to four nights in each season. At each site, a single AnaBat detector (Titley Scientific, Brendale QLD) was deployed along a vegetation edge in green space or on a waterway (wetland/creek). Vegetation edges can be areas of high bat activity (Gonsalves et al. 2012) with bats using these edges as navigation beacons (Limpens et al. 1989; Verboom and Huitema 1997). To reduce the risk of vandalism of equipment, AnaBat detectors were placed inside budgie boxes and attached to trees at a height of 3 m, with ultrasonic microphones orientated horizontally (i.e., parallel to the ground) (Figure 2a). However, at ‘waterway’ sites, AnaBat detectors were discretely placed on the ground and within vegetation adjoining the waterway. Microphones for these detectors were orientated to face the waterway from a height of <0.5m from the water surface (Figure 2b). This was done to maximise the chance of detecting Large-footed Myotis (Myotis macropus), a low-flying trawling bat species (see Gonsalves and Law in press). Each detector recorded bat calls from dusk until dawn for up to four consecutive nights each month. Since bat activity can be significantly reduced during heavy rain, sampling avoided these conditions. All recorded bat calls were identified to species using automated call identification software, AnaScheme (Adams et al. 2010), in association with an identification key for bats of Sydney (unpublished data – B. Law). Bat calls with fewer than three valid pulses (i.e., minimum of six data points and model quality of ≥0.9) were not analysed by AnaScheme. Because multiple bat species may call simultaneously, calls were assigned to a species only if >50 % of pulses within the sequence were attributed to that species and only calls with a minimum of three pulses classified to the same species were identified. All bat calls that could not be assigned to a bat taxon were included in counts of total bat activity, but were labelled as ‘unidentified’. Since linear calls of M. macropus and Long-eared Bats, Nyctophilus spp., can be difficult to distinguish using automated software, all linear calls were assigned an identification of ‘linear bat’ and were subsequently manually checked to verify whether calls were produced by Nyctophilus spp. or M. macropus.

The number of bat calls for each species and all species combined (hereafter bat activity) was tabulated by detector and night for each season of sampling. Using


SPSS version 23.0, Generalised Linear Models (GLMs) were carried out to test for the effect of site, season and the interaction of site by season on species richness, bat activity and the activity of individual species. Each model was run using a normal distribution and scaled identity function.

10 / Insectivorous Bats in City of Sydney

ResultsIn all, 1638 bat calls were recorded in spring 2016 (209 calls) and autumn 2017 (1429). Of these, 1231 (75 %) were identified to one of five species (Table 1). All other calls were usually poor quality and of short duration, and could not be assigned a species-level identification.

Table 1. Number of sites at which bat species were recorded in the City of Sydney in 2016-17.

Species Spring 2016 Autumn 2017Austronomus australis 2 2Chalinolobus gouldii 10 7Miniopterus schreibersii oceanensis+ 3 9Mormopterus ridei 5 5Myotis macropus+ 2 3+ Denotes species listed as threatened under the NSW Threatened Species Conservation Act 1995.

Nightly species richness (number of bat species per night) was significantly affected by site (F11,30=17.244, P<0.0001), season (F1,30=12.691, P=0.001) and the interaction of site by season (F11,30=3.668, P=0.002). Nightly richness across all sites was low, with 1.3±0.2 species recorded night-1. Greatest nightly richness was recorded at Sydney Park (2.6±0.5 species night-1), followed by Federal Park (2.3±0.5), Rushcutters Bay Park (2.3±0.5) and Woolloomooloo Bay (2.2±0.5), while <2 species night-1 were recorded at all other sites (Figure 2). Nightly richness was greater in autumn 2017 compared to spring 2016 at Kimberley Grove, Centennial Park, Rushcutters Canal, Rushcutters Bay Park and Sydney Park (Figure 3). However, nightly richness was greater in spring 2016 compared with autumn 2017 at Sydney Park Wetland and Waterfront Park (Figure 3).

Spring 2016Autumn 20175

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Figure 3. Nightly species richness at each sampling site in spring 2016 and autumn 2017.

Bat activity (number of bat calls per night) was significantly affected by site (F11,30=23.299, P<0.0001), season (F1,30=29.738, P<0.0001) and the interaction of site by season (F11,30=17.997, P<0.0001). Bat activity across all sites was 30.3±9.9 calls night-1. Greatest bat activity was recorded at Woolloomooloo Bay (104.4±76.4 calls night-1), followed by Sydney Park (104.0±51.3), Rushcutters Bay Park (73.0±47.1), Rushcutters Canal (20.5±12.2), Federal Park (14.5±1.6) and Sydney University (10.8±3.2), while <10 calls night-1 were recorded at all other sites (Figure 4). Bat activity was greater in autumn 2017 compared to spring 2016 at Kimberley Grove, Rushcutters Canal, Rushcutters Bay Park, Sydney Park and Wolloomoolloo Bay (Figure 4). However, total bat activity was greater in spring 2016 compared to autumn 2017 at Sydney Park Wetland (Figure 4).

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Figure 4. Nightly bat activity at each sampling site in spring 2016 and autumn 2017.

Gould’s Wattled Bat (Chalinolobus gouldii) activity was significantly affected by site (F11,30=15.740, P<0.0001), season (F1,30=14.879, P=0.001) and the interaction of site by season (F11,30=15.109, P<0.0001). Nightly activity of C gouldii across all sites was 10.69 calls night-1. Greatest nightly C. gouldii activity was recorded at Sydney Park (75.8±39.9 calls night-1), followed by Rushcutters Bay Park (35.0±26.2), Rushcutters Bay Canal (3.8±2.3) and Federal Park (3.0±1.5), while <3 calls night-1

were recorded at all other sites (Figure 5). Nightly C. gouldii activity was greater in autumn 2017 compared to spring 2016 at Rushcutters Canal, Rushcutters Bay Park and Sydney Park (Figure 5). However, nightly C. gouldii activity was greater in spring 2016 compared to autumn 2017 at Federal Park, Sydney Park Wetland 4, Victoria Park and Woolloomooloo Bay (Figure 5).

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Figure 5. Chalinolobus gouldii bat activity at each sampling site in spring 2016 and autumn 2017.

Eastern Bentwing Bat (Miniopterus schreibersii oceanensis) activity was significantly affected by site (F9,30=335.893, P<0.0001), season (F1,30=299.756, P<0.0001) and the interaction of site by season (F9,30=302.491, P<0.001). Nightly activity of M. schreibersii oceanensis across all sites was 2.0±0.7 calls night-1. Greatest nightly M. schreibersii oceanensis activity was recorded at Rushcutters Bay Park (13.0±7.2 calls night-1), followed by Sydney Park (3.8±2.5) and Federal Park (2.8±1.3), while <2 calls night-1 were recorded at all other sites (Figure 6). Nightly M. schreibersii oceanensis activity was greater in autumn 2017 compared with spring 2016 at all sites, with the species recorded at low levels of activity (<1 call night-1) at just three sites in spring 2016 (Figure 6).

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Figure 6. Miniopterus schreibersii oceanensis activity at each sampling site in spring 2016 and autumn 2017.

Eastern Freetail Bat (Mormopterus ridei) activity was significantly affected by site (F8,30=9.608, P<0.0001) and the interaction of site by season (F7,30=5.528, P<0.0001), but not season alone (F1,30=3.639, P=0.066). Nightly activity of M. ridei across all sites was 1.0±0.6 calls night-1. Greatest nightly M. ridei activity was recorded at Sydney Park (7.0±6.0 calls night-1), followed by Rushcutters Bay Park (2.0±1.1) and Federal Park (1.3±0.5), while <1 calls night-1 was recorded at all other sites (Figure 7). Nightly M. ridei activity was greater in autumn 2017 compared with spring 2016 at Federal Park, Centennial Park, Rushcutters Canal, Rushcutters Bay Park and Sydney Park (Figure 7). However, nightly M. ridei activity was greater in spring 2016 compared with autumn 2017 at Sydney University and Woolloomooloo Bay (Figure 7).

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Figure 7. Mormopterus ridei activity at each sampling site in spring 2016 and autumn 2017.

Myotis macropus activity was significantly affected by site (F3,9=6.384, P=0.013), season (F1,9=14.383, P=0.004) and the interaction of site by season (F2,9=7.224, P=0.013). Nightly activity of M. macropus across all waterway sites was 22.0±17.3 calls night-1. Greatest nightly M. macropus activity was recorded at Woolloomooloo Bay (91.0±73.4 calls night-1), followed by Rushcutters Canal (6.8±3.8) and Centennial Park (0.6±0.6), while the species was not recorded at Alexandria Canal or Sydney Park Wetland 4 (Figure 8). Nightly M. macropus activity was greater in autumn 2017 compared with spring 2016 at all sites where the species was recorded (Figure 8).

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Figure 8. Myotis macropus activity at each waterway sampling site in spring 2016 and autumn 2017.

White-striped Freetail Bat (Austronomus australis) activity was infrequently (<1 call night-1) recorded during the survey at Alexandria Canal, Centennial Park and Sydney Park. Consequently, no statistical analysis could be undertaken for this species.

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DiscussionAcoustic surveys in spring 2016 and autumn 2017 in the City of Sydney LGA identified five insectivorous bat species, of which two are listed as threatened under the NSW Threatened Species Conservation Act 1995. The bat assemblages recorded in small patches of bushland/green space embedded within City of Sydney’s highly urbanised matrix contrasts with other studies that have described richer bat communities persisting in leafier suburbs (Hourigan et al. 2006; Hourigan et al. 2010; Basham et al. 2010) or in smaller urban centres with moderate neighbourhood vegetation cover and proximity to remnant vegetation (Luck et al. 2013). Bat activity levels in spring 2016 (~7 calls night-1) were 50 % lower than levels recorded for other urban areas and 75 % lower than urban bushland across the Sydney Metropolitan area (Threlfall et al. 2011). Activity in autumn 2017 (~60 night -1) was comparable to activity recorded in bushland of nearby North Sydney in the same season (Gonsalves and Law 2014). Bat activity and the activity of individual species was greatest in autumn.

Bat species diversityBat species richness (~1.3 species night-1) in the City of Sydney LGA was low, but comparable to urban areas in the Sydney Metropolitan area. This is likely to be related to the small extent of bushland in the LGA and the hostile matrix formed by this highly urbanised part of Sydney. Five echolocating bat species were recorded during the study, including two threatened species (M. schreibersii oceanensis andM. macropus). All species had previously been recorded in the LGA, with most species recorded in the Royal Botanic Gardens precinct (Bionet, accessed May 2017). Chalinolobus gouldii was widespread and recorded at all 12 sampling sites (10 in spring and seven in autumn), while M. schreibersii oceanensis was also relatively widespread and recorded at nine sampling sites (three in spring and nine in autumn). Mormopterus ridei was less widespread and recorded at seven sites (five in spring and autumn, respectively), while A. australis was infrequently recorded at just three sites (two in spring and autumn, respectively) in the LGA. Myotis macropus was recorded at three of five waterway sites (two in spring and three in autumn).

Interestingly, species that are somewhat common in other parts of Sydney were rare or absent in the City of Sydney LGA. The Little Forest Bat (Vespadelus vulturnus) was not recorded during our surveys yet has been recorded in bushland of northern Sydney (Basham et al. 2011). An unconfirmed acoustic record for the species at Sydney University was reported during council’s 2012 baseline data collection. However, this record received a confidence level of ‘possible’, indicating that call characteristics were comparable with the species, but there was a reasonable probability of confusion with one or more similar species (Mills et al. 1996). Vespadelus vulturnus is known to select dead trees offering many hollows (Campbell et al. 2005), which appear to be scarce in the LGA (pers. obs. - L. Gonsalves). Mormopterus ridei is also frequently recorded in Sydney (Basham et al. 2011; Threlfall et al. 2012a), but was rarely detected in the City of Sydney LGA and in the nearby North Sydney LGA (Gonsalves and Law 2014). In a study conducted in the more ‘leafy’ northern suburbs of Sydney (representing Pittwater, Warringah, The Hills, Hornsby and Ku-ring-gai LGAs), average tree diameter, hollow abundance and amount of bushland within 3 km were the most important variables predicting the activity of this species, with activity positively related to these variables (Basham et


al. 2011). Given there is a limited number of tree hollows in the LGA, as well as the highly fragmented nature of bushland, it is not surprising that this species was rarely recorded during our surveys. Additionally, M. ridei is more likely to occur in areas with soils of higher productivity (McConville et al. 2014). The geology Sydney is heavily dominated by Hawkesbury Sandstone, which is considered to be nutrient- poor (Benson and Howell 1995).

The East-coast Freetail Bat (M. norfolkensis), is morphologically similar to the Eastern Freetail Bat, with both species considered to be open-space bats (McConville et al. 2014). However, M. norfolkensis was not recorded in the LGA. A study of the distribution of three morphologically similar species (including M. norfolkensis and M. ridei) in the Hunter and Central Coast regions of NSW identified that the former was more likely to occur in areas with a lack of urban development (McConville et al. 2014). The absence of M. norfolkensis in the highly urbanised City of Sydney LGA supports the predictions that this species is urban-sensitive (McConville et al. 2014). However, the species has been recorded in highly urbanised areas on the Cumberland Plain (Gonsalves and Law 2016) and on the Northern Beaches (pers. comm. – B. Law), particularly near wetlands.

The Southern Forest Bat (Vespadelus regulus) is another species that was previously recorded as part of council’s baseline data collection in 2012, but not recorded during this survey. It is highly unlikely that the species occurs in the LGA as at this latitude it is restricted to higher elevations (pers. obs. B. Law). In Sydney, calls of this species entirely overlap in frequency with M. schreibersii oceanensis (Pennay et al. 2004) and are likely to have been misidentified during the 2012 baseline surveys.

The Little Bentwing Bat (Miniopterus australis) has also previously been infrequently recorded in the LGA yet was not recorded during our survey. This species was recorded in nearby North Sydney, but only infrequently and restricted to a single site that provided roosting habitat (stormwater culvert) (Gonsalves and Law 2014). It is possible that surveys undertaken near potential roosting sites may record the species.

Bat activityWith the exception of a single site (Sydney Park), which had higher than average bat activity in spring for urban areas of Sydney (Threlfall et al. 2011), bat activity levels across the LGA were low (~7 calls night-1). Bat activity across all sites and seasons was 30.3±9.9 calls night-1. However, hotspots of activity were identified during our surveys. For example, bat activity recorded at Woolloomooloo Bay (104.4±76.4 calls night-1), Sydney Park (104.0±51.3) and Rushcutters Bay Park (73.0±47.1) were 2.5-3.5 times higher than the LGA average. Two of these sites are moderately large green spaces with some tree cover providing vegetation edges and large fig trees that may be used as roosts by some bat species. Two frequently recorded species at these sites were C. gouldii and M. schreibersii oceanensis, both of which are considered to be edge-space foraging bats (Adams et al. 2009; Threlfall et al. 2011). The third site that represented a hotspot of bat activity in the LGA was Woolloomooloo Bay. Bat activity at this site was dominated by M. macropus, a trawling species that is known to forage at this site (Gonsalves and Law in press) and on the nearby ponds in the Royal Botanic Gardens (pers. obs. – L. Gonsalves).


On average across the LGA, bat activity was greater in autumn 2017 than spring 2016, and this was particularly the case at some sites (Kimberley Grove, Rushcutters, Rushcutters Bay Park, Sydney Park and Woolloomooloo Bay). The greater level of activity recorded in autumn is likely to be a reflection of increased activity by C. gouldii and M. schreibersii oceanensis. Miniopterus schreibersii oceanensis was only recorded at three sites in spring 2016 with low levels of activity (<1 pass night-1), whereas the species was recorded at nine sites in autumn 2017. The abundance of this species in Sydney is greatest during autumn when these bats prepare for overwintering by congregating in dispersed subterranean roosts around Sydney (Hoye and Spence 2004; Gonsalves and Law 2014). In summer, adult females of this species are known to migrate just prior to summer to one of three known maternity caves in NSW, where they give birth to and care for young (Dwyer 1963). The young are weaned ~6 weeks after birth when the adult females disperse from maternity caves, soon followed by the weaned young (Dwyer 1963). In nearby North Sydney, M. schreibersii disperses from a major overwintering roost in mid- spring and it is likely that reduced activity in the City of Sydney LGA in spring 2016 is due to fewer individuals being present as a result of the exodus of adult females to maternity caves.

At Woolloomooloo Bay, elevated levels of activity in autumn 2017 relative to spring 2016 reflected increased activity of M. macropus (~225 calls night-1; 45 times spring activity levels). This result contrasts with findings for the species in nearby North Sydney where there was a trend for greater activity in summer relative to other seasons. This species is known to produce two litters of single young each year in October/November and January/February (Churchill 2009). It is possible that elevated activity levels for M. macropus in autumn 2016 reflected an increase in the number of individuals in the population as young from the second litter become weaned and begin to forage. Additionally, elevated activity levels may be indicative of a nearby, seasonally used, roosting site. Follow-up dusk surveys may be able to confirm whether a roosting site occurs in Wolloomoolloo Bay.


Management recommendationsDespite containing relatively small areas of green space/bushland that are highly fragmented, the City of Sydney LGA supports five insectivorous bat species, two of which are listed as threatened species in NSW. Consequently, management of habitats used by these species as well other aspects of their ecology is of importance. Below we provide recommendations for management and future research pertinent to bat roosting, foraging as well as other aspects of bat ecology in the LGA.

Roosting habitatThe City of Sydney LGA is used by M. schreibersii oceanensis which was widespread in autumn 2017. The species is known to congregate and overwinter in Sydney in autumn and winter, using an abundance of artificial subterranean structures that are present (e.g., stormwater culverts, disused tunnels) (Hoye and Spence 2004; Bonsen 2012; Gonsalves and Law 2014). However, no roosts are known for the species in the City of Sydney LGA. Future surveys of artificial structures known to be used by the species should be undertaken using acoustic detectors and thermal imaging in autumn. In particular, surveys should target box culverts. Locating roosting sites for M. schreibersii oceanensis is important as these are critical resources for bats.

In the absence of known roosting sites for the species, the precautionary principle should be adopted and steps taken to conserve potential roost sites (e.g., maintenance of culverts and provision of guidelines for timing of maintenance works). The largest M. schreibersii oceanensis roost recorded in Sydney (a disused railway tunnel in North Sydney used by up to 2000 bats) was previously abandoned in 1995, presumably due to human disturbance (Hoye and Spence 2004). It is therefore important to sensitively manage potential roosting habitat within the LGA. This includes taking steps to ensure the structural integrity of potential roost sites to avoid collapse at roost entrances and prevent injury or mass entombment of bats, while taking great care to minimise disturbance to roosting bats. Disturbance of overwintering bats can result in expenditure of energy reserves that are otherwise needed through winter when prey are known to be less abundant. Given M. schreibersii oceanensis is most abundant in Sydney in autumn and winter prior to dispersal in spring (Hoye and Spence 2004; Gonsalves and Law 2014), maintenance of potential roost sites (e.g., culvert works) should avoid these periods. Additionally, dusk surveys should be undertaken prior to commencement of works to ensure bats are not roosting within the structure. To minimise the risk of flooding in culverts, removal of sediment should be undertaken periodically, but should occur when bats are not using the structure for roosting.

Myotis macropus is known to roost in artificial structures near water (e.g., wharves, stormwater culverts, bridges) in Sydney (Gonsalves and Law in press). Elevated levels of activity for the species in autumn 2017 may be indicative of nearby roosting sites. Follow-up dusk surveys may be able to confirm whether roosting sites occur in Wolloomoolloo Bay and in a sandstone-lined drain that extends beneath Rushcutters Bay Park. Similar roosting sites have been identified elsewhere in Sydney Harbour (Gonsalves and Law in press). Locating roosting sites for the species in the LGA would be significant as only two other roosting sites are known in the Sydney estuary (Gonsalves and Law in press).


While a number of artificial roosting sites are likely to occur in the LGA, roosts for tree hollow using species are likely to be limited. Chalinolobus gouldii was one tree- hollow roosting species that was commonly recorded flying in the LGA. This species is known to roost in dead spouts in living River Red Gum, Eucalyptus camuldulensis, in farmland–remnant vegetation mosaics and adjacent forested floodplains in south- eastern Australia (Lumsden et al. 2002). Elsewhere, the species has also been recorded roosting in tree stumps, bat boxes and buildings (Churchill 2009). While the species has been recorded roosting in fig trees in the Royal Botanic Gardens (pers. comm. – J. Martin) and Centennial Park (pers. obs. - B. Law), further research should be undertaken to identify where tree-hollow using species, such as C. gouldii, do roost within the LGA. Hollow trees are considered to be a limiting resource in urban bushland, increasingly so because of potential competition from overabundant and aggressive parrots (e.g., Rainbow Lorikeet, Trichoglossus haematodus) (Basham et al. 2011; Threlfall et al. 2013a). Supplementary roosts in the form of bat boxes are readily used by Gould’s Wattled Bat in Sydney (Fletcher 2014), but careful consideration needs to be given to design features to allow use by other species and the consequences to other bats of increasing the abundance of C. gouldii. Black rats Rattus rattus are also likely to be a predatory threat at roosts of small bats (Threlfall et al. 2013c). Consequently, management of rats may be important near significant bat roosts.

Foraging habitatFive echolocating bat species were recorded in the LGA during the study. Of these, two are considered to be edge space species (C. gouldii and M. schreibersii oceanensis), one an open-space (M. ridei), one an above-canopy (A. australis) and one a specialised trawling (M. macropus) foraging strategy over water (Churchill 2009).

Chalinolobus gouldii and M. schreibersii oceanensis activity was greatest at sites that provided a vegetation edge for these species (i.e., Sydney Park, Rushcutters Bay Park). In many landscape mosaics, edge habitats, especially wide tracks penetrating forests, are areas of high bat activity (Law and Chidel 2002; Menzel et al. 2002; Lloyd et al. 2006; Gonsalves et al. 2012), representing navigational aids (Limpens et al. 1989; Verboom and Huitema 1997), supporting high concentrations of small swarming prey (Verboom 1998; Pavey et al. 2001) and potentially providing protection from predation. Chalinolobus gouldii and M. schreibersii oceanensis are often observed up to 50 m distant from edges (pers. obs. - authors), suggesting gaps and spaces between vegetation are likely to be important. The contribution of mown versus naturally grassed ground covers is not known for these species. Reduced insect diversity occurs in the most intensively built areas of urban areas (Denys and Schmidt 1998, McIntyre 2000), with these areas supporting half the diversity present in rural and/or natural areas (McKinney 2002). In urban landscapes of the Sydney metropolitan region, approximately three times more insect biomass has been recorded in urban bushland than in open spaces (Threlfall et al. 2012b). Urban areas generally contain low vegetation cover with reduced plant diversity. Increasing the diversity of plants in the City of Sydney LGA may help to increase the diversity of insect prey available to C. gouldii and M. schreibersii oceanensis. Furthermore, both species are known to tolerate and forage near artificial lights. Chalinolobus gouldii activity is five times higher in lit areas within urban bushland compared with unlit areas (Threlfall et al. 2013b). Mormopterus ridei is another species with higher activity (two orders of magnitude) in lit areas of urban bushland (Threlfall et al.


2013b). However, some bat species are negatively affected by lighting (Stone et al. 2009), including low-lux LED (3-4 lux) street lights (Stone et al. 2012). Gould’s Long- eared Bat (Nyctophilus gouldi) was one species that was not recorded in the City of Sydney LGA and this species is known to avoid well-lit areas (Threlfall et al. 2013b). Slow-flying bat species elsewhere avoid white and green light but are equally active in darkness and in areas illuminated with red light, suggesting that red light should be used near important bat habitat requiring lighting (Spoelstra et al. 2017).

Myotis macropus was recorded at three of five waterway sites surveyed. Alexandria Canal, a concrete channel with abundant surface water, was one site where the species was not detected. In Western Sydney, surveys for this species have revealed that activity on modified waterways (e.g., concrete channels) is an order of magnitude lower than natural waterways (Gonsalves and Law 2016). Artificial lighting also affects M. macropus activity (Gonsalves and Law 2016), so the amount of lighting provided at wetlands or other areas supporting hot-spots of activity should be carefully considered. Myotis macropus was also not recorded at Sydney Park Wetland during our survey, despite the species being recorded on ponds/wetlands elsewhere in the LGA (e.g., Centennial Park, Royal Botanic Gardens Ponds). A possible record of the species was collected at a nearby wetland in Sydney Park during a subsequent community bat night (pers. obs. – L. Gonsalves, April 20, 2017). The short duration of the call did not allow a confirmed identification to be made as other species in the LGA can produce steep, linear pulses in their calls when foraging or flying near clutter (e.g., flying near edge vegetation). Future surveys targeting all wetlands at Sydney Park will help to confirm whether the site is being used by the species.


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authors - cityofsydney.nsw.gov.au · web viewlloyd, a., law, b. and goldingay, r. (2006). bat...

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